1. Field of the Invention
The present invention relates to a system for accessing peripheral devices connected in a network, and in particular, a system capable of sharing devices located at nodes included in the network and capable of accessing the devices in a distributed manner. More particularly, the present invention relates to a system capable of providing a high-speed communication buffering control function and a high-speed communication bus window control function for accessing peripheral devices connected in a network.
2. Description of the Related Arts
The inventors of the present invention know that the system for accessing peripheral devices connected in a network designed to build driver software in an operating system and to load within the driver software a virtual peripheral device system having the different configuration rather than the actual peripheral device configuration for managing accesses of the actual peripheral devices.
The inventors of the present invention know that another system for accessing peripheral devices connected in a network designed to build the virtual peripheral device system configured from two or more managing areas for managing accesses of the actual peripheral devices.
In the following parts, an operation of one of the above-mentioned systems for accessing peripheral devices connected in the network will be described. The accessing system transmits a large volume of data through the network.
Herein, a term "node" is used for each networked terminal point such as a computer, a word processor, and a workstation. A term "peripheral device" is used for each device connected to each node. Further, a term "network peripheral device" is used for peripheral devices located at nodes connected through the network.
At first, a network peripheral device managing unit on a starting node issues a request for accessing a peripheral device excluded in its own node, and then issues a request for reading the allowable amount of data to be transmitted in one call through the network.
The network peripheral device managing unit on a receiving node receives the request and writes it in the managing unit itself. Then, the network peripheral device managing unit serves to analyze protocol, to process accessing procedure of a peripheral device, to create a response protocol on the basis of the accessed result, and to transmit the response protocol to the network peripheral device managing unit on the starting node.
The network peripheral device managing unit on the starting node serves to receive the response protocol, to store the data contained in the response protocol, to determine whether or not all the requested data is read, if not, it returns to the first step, that is, issuing the request for accessing the peripheral device again, and if yes, it terminates the operation.
This known accessing system will be described in more detail in the following parts with reference to FIGS. 1 and 2. The first and the second known network accessing system, as shown in FIG. 2, includes an application 10, other management 11, a peripheral device management 12, a communication management 13, a peripheral device 14 on a starting (sending) node S1, and other management 17, a communication management 18, a peripheral device management 19, a peripheral device 20 on an accessing (receiving) node S2. Both nodes S1, S2 are connected with each other through a network 15, and are controlled by an operating system (OS) 16.
The above-mentioned first network accessing system is designed to build driver software in an operating system and to load within the driver software a virtual peripheral device system having the different configuration rather than the actual peripheral device configuration for managing accesses of the actual peripheral devices.
Referring to FIGS. 1 and 2, an operation of the network accessing system will be described. At first, a network peripheral device management 12 on a starting node S1 issues a request for accessing a peripheral device excluded in its own node's peripheral device 14 (step ST1) and then a request for reading the allowable amount of data (step ST2) to be transmitted in one call through the network 15 (step ST3). The network peripheral device management 19 on a receiving node S2 receives the request and writes it in itself (step ST4). Then, the network peripheral device management 19 serves to analyze protocol (step ST5), to process accessing procedure of a peripheral device 20 (step ST6), to create a response protocol on the basis of the accessed result (step ST7), and to transmit the response protocol to the network peripheral device management 12 on the starting node S1 (step ST8).
The network peripheral device management 12 on the starting node S1 serves to receive the response protocol (step ST9) to store the data contained in the response protocol (step ST10), to determine whether or not all the requested data is read (step ST11), if not, it returns to the first step (step ST12), that is, issuing the request for accessing the peripheral device 20 again, and if yes, it terminates the operation (step ST13).
Until the reading of all the data is terminated, the steps ST2 to ST11 are repeated. In the process, the communication management 13 has a function of dividing the data into the allowable amount of the data to be sent out in one call through the network 15.
In the next parts, the other one of the above-mentioned systems for accessing peripheral devices connected in the network will be described. The accessing system transmits a large volume of data through the network.
A network peripheral device managing unit on a starting node issues a request for accessing a peripheral device excluded in its own node. Then, the network peripheral device managing unit serves to create a protocol, to divide the protocol, and to pass the divided protocol to a communication managing unit on the starting node. The communication managing unit on the starting node transmits the divided protocol to a communication managing unit on a receiving node. The transmission of the divided protocol between the communication managing units of the starting node and the receiving node is repeated until the total protocol has been transmitted and received.
The later process is likewise to the process described in the former known accessing system. That is, the network peripheral device managing unit on the receiving node serves to analyze the protocol, to execute accessing of the peripheral device, to create a response protocol on the basis of the accessed result, and to transmit the response protocol. The network peripheral device managing unit on the starting node serves to receive the response protocol, to store the data, to determine whether or not all the requested data is read, if not, it returns to the first step, that is, issuing the accessing request again, and if yes, it terminates the process. In the process, the network peripheral device manager on the starting node serves to divide the data into the allowable amount of data to be transmitted in one call through the network.
This latter known accessing system will be described in more detail in the following parts with reference to FIGS. 2 and 3.
The second known system concerns with the network peripheral device accessing system which is designed to build the virtual peripheral device system configured from two or more managing areas for the purpose of managing accessing of the actual peripheral devices.
With reference to FIGS. 2 and 3, the peripheral device management 12 on a starting node S1 which includes peripheral device 14 issues a request for accessing a peripheral device excluded in its own node (step SU1). Then, the peripheral device management 12 serves to create a protocol, to divide the protocol (step SU2), and to pass the divided protocol to a communication management 13 on the starting node S1. The communication management 13 on the starting node S1 transmits the divided protocol to a communication management 18 on a receiving node S2 (SU3). The transmission of the divided protocol between the communication managements 13, 18 of the starting node S1 and the receiving node S2 is repeated until the total protocol has been transmitted and received (SU4).
The later process is similar to the process shown in FIG. 1. That is, the network peripheral device management 19 on the receiving node S2 serves to analyze the protocol (step SU5), to execute accessing of the peripheral device 20 (step SU6), to create a response protocol on the basis of the accessed result (step SU7), and to transmit the response protocol (step SU8). The network peripheral device management 12 on the starting node S1 serves to receive the response protocol (step SU9), to store the data (step SU10), to determine whether or not all the requested data is read (step SU11), if not, it returns to the first step, that is, issuing the accessing request again, and if yes, it terminates the process (step SU12). In the process, the network peripheral device management 12 on the starting node S1 serves to divide the data into the allowable amount of data to be transmitted in one call through the network 15.
The aforementioned two accessing systems may apply to a system for accessing a console located on each node.
However, the above-mentioned accessing systems have the following disadvantages. At first, those systems are required to load a different software system for managing peripheral devices in place of the software used on the traditional operating system, that is, it results in disadvantageously changing the current software resource.
Second, the former known accessing system requires a lot of memory area for realizing the virtual peripheral device system. It results in disadvantageously making the memory area of the system located at each node larger.
Third, the latter known accessing system, on the other hand, requires a small memory area. The division of the protocol on the starting node results in bringing about more frequent communication between the peripheral device managing unit and the communication managing unit and increasing the communications in number, which leads to an appearance of a large overhead.
Further, the both accessing systems require the starting node to wait for the response protocol from the receiving node. It means that the waiting time of the peripheral device management gives a great burden to the peripheral management for the system located at the starting node.
Moreover, the latter accessing system needs to prepare on both of the starting and the receiving nodes a memory area for storing the data to be communicated. The memory area of the starting node is obtainable, because the application run on the node operating system is capable of storing the data. In the receiving node, the node operating system itself has to provide the memory area. The memory area is not negligible and may often give pressure on the memory area to be used for the application.
The foregoing disadvantages are true to the case where those known accessing systems apply to accessing a console located on each node.
In turn, the description will be directed to a high-speed communication buffering control system such as a local area network relevant to the present invention and the foregoing peripheral device or console accessing systems. The currently available local area network (referred to as LAN) means a system including two or more nodes such as a computer, a video display terminal, a workstation and a print server connected through a network in an organic manner.
Currently, on the LAN, each hierarchical layer has been standardized so that a file or a job can be transferred through the LAN in a standard manner.
As a common hierarchical model, it is well known that the International Standardization Organization (ISO) provides an Open Systems Interconnection (OSI) reference model (See the Table 1 as a reference).
TABLE 1 ______________________________________ Level 7 Application Protocol (User level, that is, service and procedure depending on the application program) Level 6 Presentation Protocol (Data format, code, and conversion and encryption of data) Level 5 Session Protocol (Interaction between processes, segmentation, control of buffering) Level 4 Transport Protocol (Control communication between terminals, disassembling and assembling a message, and control of priority) Level 3 Network Protocol (Management of a network, organizing block and basket, message format) Level 2 Link Protocol (Initialization, control, stop, and error recovery of data flow) Level 1 Physical Protocol (Electric interface) ______________________________________
The OSI reference model includes seven layers (protocol) from the communication layer depending on the control of a communication line to the layer depending on business. The seven layers consist of an application layer (level 7), a presentation layer (level 6), a session layer (level 5), a transport layer (level 4), a network layer (level 3), a link layer (level 3), and a physical layer (level 1) ranged in sequence from the top layer.
The LAN communication protocol includes, for a sending node, an application layer and a presentation layer, a session layer, a transport layer, a network layer, a data link layer, all for the client node, and a physical layer. For a receiving node, the LAN communication protocol includes a data link layer, a network layer, a transport layer, a session layer, an application layer, and a presentation layer, all arranged in data-transmitting sequence.
The aforementioned LAN communication protocol takes the following communication procedure between the sending node and the receiving node on the basis of the hierarchical protocol.
At the sending node, the data to be sent is created on the protocols of the application layer and the presentation layer. Then, at the session layer,a session level header is added to the data. At the transport layer, a transport level header is added to the data. At the network layer, a network level header is added to the data. Last, at the data link layer, a data link level header is added to the data.
The resulting data is sent to the receiving node through an interface unit defined by a physical layer and a transmission medium.
At the receiving node, the data link level header, the network level header, the transport level header, and the session level header are removed from the data in reverse sequence.
Lastly, the data are represented at the application layer and the presentation layer.
Those headers are used as control information. Those headers allow the present LAN to be connected with the other two or more LAN. That is, those headers provide inter-operativity among the LANs.
Each node is configured so that a plurality of protocol software modules are allowed to be linked. Between the hierarchical layers, the data are copied from the layer to the layer.
However, the foregoing LAN system is designed to copy the same data at each hierarchical layer, resulting in increasing the memory areas for the data, making the copying time longer than the protocol processing time, thereby lowering the execution speed. Further, as the data go up from the upper layer to the lower layer, the data to be transferred are excessively pressed within a packet.
Moreover, in case all the layers are standardized, all the protocols of two or more classes are required to be implemented. In actuality, the same software is used on the common portion of the classes without creating the software for each class. Hence, as the classes are increased in number, the process flow for selecting a class appears more frequently, which results in causing an overhead.
The foregoing LAN system provides so large a header at each layer that the effective transmission efficiency of the data to be sent out to a transmission path is made lower. In addition, as the LAN has a lot of hierarchical layers, the processing time becomes longer.